/*
 * Copyright 2002-2017 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.springframework.beans.factory.config;

import java.util.LinkedHashSet;
import java.util.Set;

import org.springframework.beans.BeanUtils;
import org.springframework.beans.TypeConverter;
import org.springframework.core.ResolvableType;
import org.springframework.lang.Nullable;

/**
 * Simple factory for shared Set instances. Allows for central setup
 * of Sets via the "set" element in XML bean definitions.
 *
 * @author Juergen Hoeller
 * @see ListFactoryBean
 * @see MapFactoryBean
 * @since 09.12.2003
 */
public class SetFactoryBean extends AbstractFactoryBean<Set<Object>> {

    @Nullable
    private Set<?> sourceSet;

    @SuppressWarnings("rawtypes")
    @Nullable
    private Class<? extends Set> targetSetClass;


    /**
     * Set the source Set, typically populated via XML "set" elements.
     */
    public void setSourceSet(Set<?> sourceSet) {
        this.sourceSet = sourceSet;
    }

    /**
     * Set the class to use for the target Set. Can be populated with a fully
     * qualified class name when defined in a Spring application context.
     * <p>Default is a linked HashSet, keeping the registration order.
     *
     * @see java.util.LinkedHashSet
     */
    @SuppressWarnings("rawtypes")
    public void setTargetSetClass(@Nullable Class<? extends Set> targetSetClass) {
        if (targetSetClass == null) {
            throw new IllegalArgumentException("'targetSetClass' must not be null");
        }
        if (!Set.class.isAssignableFrom(targetSetClass)) {
            throw new IllegalArgumentException("'targetSetClass' must implement [java.util.Set]");
        }
        this.targetSetClass = targetSetClass;
    }


    @Override
    @SuppressWarnings("rawtypes")
    public Class<Set> getObjectType() {
        return Set.class;
    }

    @Override
    @SuppressWarnings("unchecked")
    protected Set<Object> createInstance() {
        if (this.sourceSet == null) {
            throw new IllegalArgumentException("'sourceSet' is required");
        }
        Set<Object> result = null;
        if (this.targetSetClass != null) {
            result = BeanUtils.instantiateClass(this.targetSetClass);
        } else {
            result = new LinkedHashSet<>(this.sourceSet.size());
        }
        Class<?> valueType = null;
        if (this.targetSetClass != null) {
            valueType = ResolvableType.forClass(this.targetSetClass).asCollection().resolveGeneric();
        }
        if (valueType != null) {
            TypeConverter converter = getBeanTypeConverter();
            for (Object elem : this.sourceSet) {
                result.add(converter.convertIfNecessary(elem, valueType));
            }
        } else {
            result.addAll(this.sourceSet);
        }
        return result;
    }

}
